Set the "reserved" timestamp when stealing a lock as well

[PayBas]

Closes #636

Maintainer checklist

Before the changes are marked as ready-for-merge:

• There is at least one (1) approval for the pull request and no outstanding requests for change.
• Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
• Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
• Proper changelog labels are set so that the changelog can be generated automatically. See also release-drafter-labels.
• If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
• java code changes are tested by automated test.

[mPokornyETM]

LGTM